An alternate method for infecting computers with ransomware signals a shift in tactics by cybercriminals that could put businesses at greater risk, according to Symantec.

A type of ransomware called Samsam has been infecting organizations but is not installed in the usual way.

"Samsam is another variant in a growing number of variants of ransomware, but what sets it apart from other ransomware is how it reaches its intended targets by way of unpatched server-side software," Symantec wrote.

It means that ransomware attackers are more directly targeting businesses and organizations to install their malware.

"The success of these recent attacks signals a shift for cybercriminals as they seek to maximize profits by setting their sights on vulnerable businesses," Symantec wrote.

Ransomware has typically been spread through drive-by downloads or spam emails with malicious attachments. The targeting of those spam emails appeared at first to be fairly random, but the success of ransomware has prompted more specific attacks.

"Ransomware has proven to be a viable business model, so it should come as no surprise that the techniques used have shifted beyond malicious spam and drive-by downloads to those more closely resembling targeted attacks," Symantec wrote.

Victims are usually asked to pay a ransom in bitcoin. The amount can range from a few hundred dollars up to thousands for businesses.

One of the latest victims of Samsam was MedStar Health, a not-for-profit organization that runs 10 hospitals in the Washington, D.C., area, reported the Baltimore Sun.

Most of its systems have been restored, but the organization has not indicated if it paid the ransom, which the newspaper reported was $18,500 in bitcoins.